Methods for use of soft continuum robotic module

ABSTRACT

A soft continuum robotic module comprises a plurality of inflatable actuators disposed between plates. Via inflation or deflation of one or more of the actuators, the module may extend, contract, twist, bend, and/or exert a grasping force. One or more modules may be combined to form a robotic arm with multiple degrees of freedom.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 17/224,809 filed Apr. 7, 2021, now U.S. Patent ApplicationPublication No. 2021-0308861 entitled entitled “SOFT CONTINUUM ROBOTICMODULE.” U.S. Ser. No. 17/224,809 claims priority to and the benefit ofU.S. Provisional Patent Application Ser. No. 63/006,358 filed on Apr. 7,2020 entitled “SOFT CONTINUUM ROBOTIC MODULE.” The contents of each ofthe foregoing applications is hereby incorporated by reference (exceptfor any subject matter disclaimers or disavowals, and except to theextent of any conflict with the express disclosure of the presentapplication, in which case the disclosure of the present applicationshall control).

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under 1800940 awarded bythe National Science Foundation. The government has certain rights inthe invention.

TECHNICAL FIELD

The present disclosure relates to actuators, and in particular to softcontinuum robotic actuators.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the following description and accompanying drawings:

FIG. 1 illustrates an exemplary soft continuum robotic module inaccordance with various exemplary embodiments;

FIG. 2 illustrates components and construction of an exemplary softcontinuum robotic module in accordance with various exemplaryembodiments;

FIG. 3 illustrates control components and diagrams of an exemplary softcontinuum robotic module in accordance with various exemplaryembodiments;

FIG. 4 illustrates sensor setup and characterization of an exemplarysoft continuum robotic module in accordance with various exemplaryembodiments;

FIGS. 5A, 5B, and 5C characterize operation of an exemplary softcontinuum robotic module in accordance with various exemplaryembodiments;

FIG. 6 illustrates motion tracking and sensing of an exemplary softcontinuum robotic module in accordance with various exemplaryembodiments;

FIGS. 7A, 7B, and 7C illustrate motion of an exemplary soft continuumrobotic module in accordance with various exemplary embodiments;

FIGS. 8A, 8B, and 8C characterize operation of an exemplary softcontinuum robotic module in accordance with various exemplaryembodiments;

FIG. 9 illustrates operation of a robotic arm comprising multiple softcontinuum robotic modules in accordance with various exemplaryembodiments;

FIGS. 10A, 10B, 10C, 10D, 10E, and 10F characterize mobility and/orpayload for an exemplary soft continuum robotic module in accordancewith various exemplary embodiments;

FIG. 11 illustrates grasping and twisting operations of an exemplarysoft continuum robotic module in accordance with various exemplaryembodiments; and

FIG. 12 illustrates a method for use of exemplary soft continuum roboticmodule in accordance with various exemplary embodiments.

DETAILED DESCRIPTION

The following description is of various exemplary embodiments only, andis not intended to limit the scope, applicability or configuration ofthe present disclosure in any way. Rather, the following description isintended to provide a convenient illustration for implementing variousembodiments including the best mode. As will become apparent, variouschanges may be made in the function and arrangement of the elementsdescribed in these embodiments without departing from principles of thepresent disclosure.

For the sake of brevity, conventional techniques and components forsoft, conformable, inflatable, wearable, and/or continuum roboticsystems and actuators may not be described in detail herein.Furthermore, the connecting lines shown in various figures containedherein are intended to represent exemplary functional relationshipsand/or physical couplings between various elements. It should be notedthat many alternative or additional functional relationships or physicalconnections may be present in exemplary soft continuum robotic moduleand/or components thereof.

Principles of the present disclosure contemplate a continuum,lightweight, multi-degree of freedom (DOF) soft robotic module 100, forexample made of high-stretch knit fabric. A set of design criteria,inspired by muscular hydrostats such as those found in elephant trunks,may be utilized in order to create a highly articulated and robust softrobotic module. An exemplary soft continuum robotic module 100 canvertically extend and twist along its central axis, as well as bend in31D space. The material properties of the knit fabrics arecharacterized. The bending articulation and payload capabilities of themodule are presented. This disclosure also demonstrates the embeddedintegration of a thin, flexible, and conductive fabric stretch sensorwith the module, for example to provide pose information for motiontracking. An on-board electropneumatic system is also disclosed. Thissystem allows for the creation of safe human-robot interfaces comprisinga multi-functional integration of multiple soft robotic modular unitsthat are deployable for various complex tasks. Moreover, exemplarysystems may be utilized to perform grasping and/or twisting operations.

With the interests in soft robotics on the rise, there have beenextensive studies of soft materials, actuation, control, sensing, andeven soft pneumatic pumps and valves. Soft robotic systems have shownadvantages of being lightweight, highly compliant, articulate, andinherently safe for interactions with the human body and environment.Thus, soft robotic systems have been developed for diverse applicationssuch as locomotion in unstructured environments, manipulation of objectswith various sizes and shapes, invasive surgical instruments, andassistive/rehabilitative devices.

Soft continuum robots are popular in manufacturing and surgical tasks aswell as activities of daily living (ADL). Such robots have been createdby combining various types of soft actuation mechanisms, includingcable-driven systems, pneumatic artificial muscles (PAMs), andinflatable actuators made of elastomers, origami, fabric, andcombinations of materials. Principles of the present disclosure showversatility and promise in applying elastomeric and woven fabricactuators to build soft continuum robotic arms that are robust,lightweight, and compliant enough to assist with ADL tasks.

However, some prior approaches have been confined to a fixed settingbecause of a tethered pneumatic source and pose sensing using a motioncapture system. For portable pneumatic systems, there have been studieson the use of pneumatic cylinders, compressed air supplies, and storagetanks to power soft robots. In order to develop compact soft robots thatare modular and deployable in outdoor applications or used aseducational toolkits, the aforementioned portable pneumatic systems canbe more bulky than necessary. Accordingly, principles of the presentdisclosure contemplate use of a compact off-board electropneumaticsystem to control the soft robotic module.

With high degree-of-freedom (DOF) continuum robots working andinteracting with the environment, there is a desire to monitor thecompliant and highly deformable nature of the soft robot in order tounderstand its locomotion capabilities as well as the inherent contactwith obstacles. Thus, proprioception and tactile feedback are desirablein controlling the movement of high-DOF continuum robots. To satisfythese desires, different types of soft sensors may be utilized, such astextile electrode-based, liquid metal-based, nanocomposite-based,optical-fiber based, and conductive yarn-based sensors.

In various exemplary embodiments, and with reference now to FIGS. 1through 6 , principles of the present disclosure contemplate a robust,compact, lightweight, and highly articulated soft robotic module 100,inspired by hydrostatic muscles. This disclosure highlights the firstsoft continuum robot fabricated using stretch fabric, which can not onlybend in 3D space, but also vertically extend and bi-directionally twist.Folding and precision multi-layering fabrication techniques may beutilized for low-cost and rapid manufacturing of the actuator. Exemplaryembodiments utilize the concept of fabric-reinforced textile actuators(FRTAs), for example made of high-strength and high-stretch knitinflatable fabrics.

In various exemplary embodiments, a soft continuum robotic module 100comprises several inflatable actuators 105, for example as illustratedin FIGS. 1 and 7C. Additionally, module 100 may comprise variouspneumatic components, pumps, valves, electronic control modules,sensors, and/or the like, in order to govern and/or control operation ofthe inflatable actuators. The actuators may be attached at each end to aplate, for example a base plate and a top plate. Moreover, in a roboticarm, modules 100 may be connected in series, whereby the top plate of afirst module 100 is operable as the base plate of a second module 100,and so forth.

In addition to exemplary actuator 105 designs, this disclosuredemonstrates the integration of a highly stretchable, conductiveknit-fabric strain sensor 110 on the soft module. Because of sensor110's high stretchability, it is able to obtain sensory feedback forstate estimation of the knit fabric actuators 105, while still allowingactuators 105 to maintain a hyperelastic nature. Furthermore, anexemplary module 100 contains on-board electropneumatic hardware 120,wireless communication components 130, and additional IMU sensorsattached to the actuator 105. The all-inclusive on-board system andnature of module 100 allows for communication, computation, distributedsensing, actuation, and control to extend it into real-worldapplications.

Design and Fabrication

As seen in biology, muscular hydrostats are found in elephant trunks andoctopus arms, which contain muscles or fibers that are orientedlongitudinally, circumferentially, radially and/or transversely. Whenworking in tandem with one another, these fibers enable elongating,shortening, and bending motions, while helically arranged fibers createaxial torsion or twisting. Inspired by biology, exemplary embodimentsutilize a soft continuum robotic module that performs active multi-axisbending, twisting, and extending all within one actuation module. In anexemplary embodiment, each module 100 includes three extending FRTAs 105for multi-directional bending and linear elongation, and two twistingactuators for bi-directional twisting and counteracting torsionaldisturbances (for example, as seen in FIG. 2 ). The size of each softcontinuum robotic module 100 is selected so that three modules 100 caneventually be connected in series to a create a full-length softcontinuum robotic arm, which may be sized as desired (for example, tomatche the length of an average sized male arm (0.59 m)). Exemplaryembodiments also utilize highly stretchable conductive knit fabricsensors, embedded onto the skin of the knit material, to measure thestrain of the FRTAs 105 during elongation and bending.

Material Selection

Exemplary embodiments utilize a bi-directional high-stretch knitmaterial, the COTOWIN Heavy Stretch Elastic Band (Amazon.com Inc.,Seattle, WA), with a density of 850.3 kg/m³. We tested the inflatablefabric using a burst test, to find out the maximum pressure that thefabrics could withstand before failure, using the ASTM F2054 protocol.Each actuator had a similar fabric-reinforcement arrangement along thesurface. An exemplary selected material for the fabric-reinforcements isa 200D TPU-coated nylon fabric (6607, Rockywoods Fabric, Loveland, CO),with a density of 840 kg/m³. The inflatable actuator 105 is able towithstand the set maximum safety pressure of 0.69 k/Pa without bursting,thus showing high robustness and the capability of achieving increasedpayload. However, any suitable fabric and/or reinforcement may beutilized.

In exemplary embodiments, the material properties of the COTOWIN HeavyStretch Elastic Band material are characterized using the ISO-139134-1standard, where the material is stretched both in the wale and coursedirections, using a universal testing machine (UTM) (Instron 5944,Instron Corp., High Wycombe, United Kingdom). The material is testedboth with and without the fabric reinforcements. For the fabrics withoutreinforcements, in the wale direction (y-direction), parallel to thedirection of manufacturing, the fabric had a stretch of 204.94% at 8.84MPa. In the course direction (x-direction), perpendicular to thedirection of manufacturing, the stretch was much stiffer at 12.3% at32.8 MPa, exceeding the payload set by the universal testing machine of1 kN without tearing. The fabrics with reinforcements showed an increaseof overall stiffness but maintaining similar properties of the textilesat 218.77% at 8.544 MPa (in the wale direction) and 11% at 32.8 k/Pa (inthe course direction), respectively. The material properties of theconductive knit fabric (A321, LessEMF, Latham, NY) used for the anexemplary strain sensor, had a stretch of 272.65%, in the wale directionand 175.52%, in the course direction. The material properties of thewoven TPU-coated Nylon (6607, Rockywoods Fabric, CO), which was used asfabric-reinforcements in some embodiments, were determined with a linearelastic modulus: Young's modulus of E=498 MPa and Poisson's ratio ofv=0.35.

Fabrication and Integration

In various exemplary embodiments, to fabricate the soft continuumrobotic module 100 with embedded sensors, the fabrics are cut into theshape specifications using a laser cutter (Glowforge Prof, Glowforge,Seattle, WA). However, any suitable cutting device or system may beused. The different layer of fabrics, as seen in FIG. 2 , are preciselyaligned, from top-view. A heat press (FLHP 3802, FancierStudio, Hayward,CA) is used to laminate the sensor fabric, the fabric reinforcement, andthe knit base fabric layers together. The widths of the extending andtwisting actuators 105 are defined by w_(b) and w_(t), respectively. Thelaminated layered fabric in FIG. 2 is folded along the red dashed line,and sewn using high-stretch elastic thread (Maxi Lock Stretch, American& Efird, Mount Holly, NC) along the pink lines, to create the 3Dstructure seen in FIG. 2 . The sensing materials are aligned at thecenter of the fold lines to measure where the actuator extends the most.A_(1,2,3) represent the three extending actuators that inflate andextend upon pressurization, as seen in FIG. 2 .

Due to the centralized strain-limiting layer created by the pink sewnlines seen in FIG. 2 , the actuators, A_(1,2,3), will bend when inflatedseparately or in pairs, but will extend when all three are inflatedtogether. The bi-directional twisting actuators (A_(4,5)) aremanufactured separately and added to the stem of the soft continuumrobotic module as shown in FIG. 2 . For the twisting actuators, thefabric reinforcements are angled at the desired twisting angle α=30° forcounterclockwise motion (actuator A₄) and α=−30° for clockwise motion(actuator A₅), as seen in FIG. 2 ). Because of the high collapsibilityand almost zero initial stiffness of fabrics, two twisting actuators areable to fit within the central space of the actuator (as seen in FIG. 2), allowing for a compact design of the bidirectional twistingactuators. The width of the extending and twisting actuators are definedby w_(b) and w_(t) correspondingly.

Electronics and Hardware

Exemplary embedded hardware allows independent sensing and control ofeach soft robotic module 100. To this end, a four-layered system isencased within a cylindrical box (radius=60 mm, height=140 mm), as seenin FIG. 1 . As shown in FIG. 3 , an exemplary control unit is designedusing off-the-shelf components to regulate pressure in the fiveactuators output lines. A miniature pump (NMP830 HP,KNF Neu-berger,Inc., Trenton, NJ) is used to generate up to 0.19 MPa of sourcepressure. However, any suitable hydraulic or other suitable pressuresource may be used. The airflow of the unit is controlled by oneproportional valve (Enfield Technologies, Shelton, CT), and five 3/2-Waysolenoid valves (Miniature Solenoid Valve, Parker Hannifin, Hollis, NH).The inflation and deflation processes for each actuator are measured bya pressure sensor (ABPMANN004PGAA5, Honeywell International Inc., MorrisPlains, NJ). The orientation of the end-effector is measured by a 9-DOFinertia measurement unit (IMU) (Adafruit BNO055 Board, AdafruitIndustries, New York, NY). In some embodiments, the IMU sensor isspecifically utilized for measuring twisting and bending. Amicrocontroller (for example, a Raspberry Pi Zero W, Raspberry PiFoundation, United Kingdom) controls the pump, valves, pressure and IMUsensor on the module. It contains an onboard Wi-Fi module, allowing awireless TCP/IP communication between the module and the central PC forsending the desired pressure commands, as well as pressure and sensingmeasurements. This communication can be extended to inter-modulecommunication if necessary. An overview of an exemplary system 100 isdepicted in FIG. 3 . However, any suitable control electronics, pumps,and/or the like may be utilized, as desired.

Embedded Sensing

In some exemplary embodiments, module 100 utilizes an embedded knitstretch sensor, aligned with the three extending-bending actuators alongthe length of the actuator. When the soft module 100 bends, variableconstant curvature may be used to model the system. The lengths of thethree extending-bending actuators 105 [s₁, s₂, s₃] are estimated bytheir corresponding resistance sensor values [R₁, R₂, R₃], The areparameters of the module are defined in FIG. 6 and the arc length of thecentral axis of the module S is calculated.

A. Sensor Selection and Characterization

In order to characterize an embedded soft fabric sensor, exemplaryembodiments place the sensorized fabric on the UTM to perform loadingand unloading tests for ten cycles. To detect the resistance changes inthe conductive knit stretch sensor, a customized Wheatstone bridgecircuit may be used, as shown in FIG. 4 . The first strain cycle was notincluded in the data analysis to remove any Mullins effect. The strainrate was 96 mm/min based on the actuator's inflation rate to reach thedesired bending angle of 90°. The length of the sensor may be selectedbased on the length of the actuator (for example, 165 mm). Theforce-extension behaviors of the sensor for different widths werecalculated by varying the width along the fold of the actuator to be: 10mm, 20 mm, and 30 mm. As seen in FIG. 4 , the sensors show the maximalhysteresis values of 12.04 N, 14.87 N and 13.73 N at 60% strain, for 10mm, 20 mm and 30 mm width, respectively. The 10 mm width sensor shows ahigher sensing range and lower hysteresis in comparison. The materialhas a high stretch-to-relax time of 1.5 s and 0 s for loading andunloading. The working range of the 10 mm width sensor was maximized at26.34% strain and then the resistance begins to decrease for higherstrain values, as seen in FIG. 4 . This relationship is due to thespecific nature of the multi-material combination of the fabric sensor.Finally, the strain-resistance linear characteristic of the 10 mm sensoris shown in FIG. 4 . The results show that the fabric sensor'sresistance was proportional to the strain within its working range,where the coefficient of the determination using linear regression wasR²=0.953. The gauge factor (GF) was also calculated within the linearrange to be approximately 3.92, comparable to previous LessEMFconductive fabrics. A high GF value means the sensor has highersensitivity and is able to detect small changes in strain.

Testing an Exemplary Soft Continuum Robotic Module

In order to evaluate the capability of an exemplary soft continuumrobotic module 100, the system may be characterized for itsmaneuverability and payload capabilities. Additionally, the IMU andconductive knit stretch sensors may be evaluated, for example for statetracking and closed-loop control.

Device Characterization

In order to investigate the load performance of an exemplary softcontinuum robotic module 100, three tests for bending, extending, andtwisting tasks may be utilized. All bending and torque payload testswere performed on the UTM and each output was measured at small pressureincrements of 0.34 mpa MPa until a safety pressure of 0.207 MPa wasreached. Each experiment was repeated three times. The performancecharacteristics of an exemplary soft continuum robotic module 100 arehighlighted in Table 1.

TABLE I Performance Summary of the Soft Robotic Module PROPERTYSPECIFICATION Single actuator mass 0.03 kg Soft module mass 0.40 kgElectropneumaties' mass 1.076 kg  Contracted size 120 × 120 × 200 mmExtended size 120 × 120 × 234.38 mm Linear RoM 34.38 mm Angular RoM104.02° Single actuator torsional RoM 166.70° Soft module torsional RoM 82.70° Linear payload 231.92 ± 0.41N Bending payload  10 ± 0.27N(single side) Torsional performance 9.32 ± 0.12N (double side)   0.99 ±0.01 Nm

Bending Payload Capacity: When one side of an actuator 105 waspositioned and inflated, an exemplary module 100's maximum bendingpayload was 10.00±0.27 N, as seen in FIG. 5A. When two adjacentactuators 105 in the module were inflated to the same pressure, themaximum bending payload was noticed to be similar at 9.32+/−0.12 NV.This is comparable to lifting a weight of almost 1 kg at the actuatorlength of 0.165 m.

Torsion Torque Capacity: The twisting actuators 105 were inflated, whilebeing connected to the UTM with a string as shown in FIG. 5B. At themaximum pressure, the twisting actuators 105 in the center of module 100were capable of generating 0.98+/−0.01 Nm with a lever arm of 0.06 m asseen in Table 1. By allowing bi-directional twisting, the twistingactuators 105 are able to counteract any torsion disturbances of up toapproximately 1 Nm at the edge of module 100.

Extension Payload Capacity: In this test, the extension payload capacityof an exemplary module 100 was determined by inflating all threeactuators 105 at the same pressure, under the UTM, as shown in FIG. 5C.The maximum extension payload capacity was 231.92+/−0.41 N at 0.138 MPaas shown in Table 1.

Range of Motion

To characterize the range of motion (RoM), an exemplary soft continuumrobotic module 100 was mounted parallel to the ground. Two sets of threepassive markers were mounted at the base and top plates. For each plate,position of the center point and rotation angles are recorded by themotion capture (MOCAP) system (Optitrack, NaturalPoint Inc., Corvallis,OR). For linear elongated motion, three extending-bending actuators 105were inflated and all held at 0.207 MPa. In the bending test, only asingle extending-bending actuator 105 was inflated to 0.207 MPa. In theunconstrained twisting test, the bidirectional twisting actuator 105 wasinflated on its own, without being mounted on the soft continuum roboticmodule 100. The constrained twisting test had all the actuators 105mounted. For both twisting tests, one twisting actuator 105 was inflatedup to 0.172 MPa, while the other one was kept deflated. By inflating theother twisting actuator 105, the RoM was measured for twisting motion inclockwise and counterclockwise directions. Each experiment was conductedthree times and the averaged results for elongation, bending andtwisting are summarized and presented in Table 1.

Motion Tracking with IMU and Embedded Stretch Sensing

In various exemplary embodiments, a sensorized soft continuum roboticmodule 100 may be utilized to evaluate the sensing and controlperformance. An IMU was attached to the center of the top plate and theresistance values were measured by the embedded strain sensor, along thelength of the extending-bending actuator 105.

An experiment was conducted to compare the arc angle (θ) estimated usingthe IMU and the values obtained from the MOCAP system. The same markerset as described above was utilized for the MOCAP system. Oneextending-bending actuator 105 was inflated to 0.138 MPa and deflated to0 MPa multiple times while the orientation of the end was recorded. Asdepicted in FIG. 6 , the are angle estimate obtained using the IMU isfairly accurate with a root mean square error (RMSE) of 1.97° whencompared against the measurement from the MOCAP system.

To evaluate the length change estimation of an exemplary module 100, thethree extending-bending actuators 105 were inflated to 0.1381 MPa anddeflated to 0 MPa cyclically. From FIG. 6 , it can be observed that thechange in length of module 100 can be estimated accurately with an RMSEof 1.19 mm when the stretch sensor and MOCAP measurements are compared.

An experiment to measure the twisting angle (φ) of an exemplary module100 using both the IMU and the MOCAP was performed. One twistingactuator 105 was inflated to a pressure of 0.138 MPa and deflated to 0MPa cyclically. FIG. 6 shows that the torsion angle of the module 100can be successfully estimated using the IMU with an RMSE of 4.69°.

As disclosed herein, in various exemplary embodiments a soft continuumrobotic module 100 is robust, compliant, and highly articulated by usingcombinations of fabric-reinforced textile actuators 105. The softrobotic module 100 is capable of performing 1) multi-DOF bending usingthe combination of the three extending-bending actuators 105, 2)bi-directional twisting using twisting actuators 105 in the center ofmodule 105, and 3) extending by inflating all the extending-bendingactuators 105. A fabrication scheme is disclosed to fabricate theactuators 105 embedded with sensors, by exploiting folding and precisionmulti-layer fabrication using various 2D manufacturing methods includingheat-pressing, sewing, and laser cutting. This exemplary fabricationmethod allows one-step and rapid manufacturing of any desired number ofactuators using just folding and sewing techniques. A larger number ofactuators in a module 100 can further provide higher linear stiffnessand payload capacity while being redundant, so in these embodimentsmodule 100 would still be functional even if one or more of theactuators 105 were to fail. Accordingly, in various exemplaryembodiments 4, 5, 6, 7, 8, 10, 15, or even more actuators may beutilized.

The present disclosure also demonstrates the integration of an embeddedconductive knit stretch fabric sensor to measure the elongation of eachactuator 105. An additional IMU sensor was used to provide informationof the twisting and bending angles of the multi-DOF continuum module100. Exemplary embodiments also utilize an all-inclusive on-board systemthat includes electropneumatics and wireless communication. Thison-board system may be utilized for a robust, lightweight,fully-integrated soft continuum robotic module 100. Analytical andcomputational models for the soft continuum robotic module may becreated with continuum mechanics and finite element methods,respectively.

With reference now to FIGS. 7A, 7B, and 7C, and FIGS. 8A through 11 , invarious exemplary embodiments, module 100 is configured to implement acontracting and/or twisting motion. In some embodiments, module 100implements these motions using only three actuators 105.

In some embodiments, each soft continuum robotic module 100 includesthree bending FRTAs 105, as seen in FIGS. 7A, 7B, and 7C. Thefabrication process of module 100 may be similar to those disclosedabove. This setup naturally allows module 100 to bend inmulti-directions, by inflating a single actuator 105 or two adjacentactuators 105. A difference between these exemplary embodiments andother exemplary embodiments includes that by inflating all the threeactuators 105 together, a helical twisting and contracting motionoccurs, instead of an extension motion. In accordance with principles ofthe present disclosure, this motion may occur because an inextensiblesewing line on each actuator 105 eliminates the ability for the actuator105 to extend. This leads the three actuators 105 to bend in threedifferent directions, promoting a rotational motion on the top plate andin turn forcing a twisting helical motion as the soft body of theactuators 105 collapse at the same time or similar times.

In various exemplary embodiments, performance of module 100 may beconfigured by varying the system's geometrical properties, for exampleas seen in FIG. 7C. The length of the actuators 105 (a_(l)) wasevaluated for lengths of 170, 190, 210 mm. However, any suitable lengthfor actuators 105 may be utilized. The spacing (a_(sp)) between thethree actuators 105 was evaluated for two different spacing of 22 and 77mm. Again, any suitable spacing may be utilized. The radius of theactuators 105 (a_(r)) was varied between 20, 25, 30 mm in someembodiments of module 100, but any suitable radius may be utilized. Insome embodiments, it was determined that after 103.4 kPa, the actuators105 of an exemplary module 100 with a_(r)=30 mm, started showinguncontrolled radial expansion leading to failure and the thread on theseam started peeling, before any significant twisting and contractingmotion occurred.

In some embodiments, payload tests were performed on a Universal TensileMachine (Instron 5944; Instron Corp., High Wycombe, UK). For themobility tests, two sets of passive markers were mounted at the base andtop plates of an exemplary module 100. The markers were recordedutilizing a motion capture system (Optitrack, NaturalPoint Inc.,Corvallis, OR). Each experiment was repeated three times and theactuators in module 100 were inflated at pressure intervals of 34.5 kPa.

Bending Performance

In some exemplary embodiments, in a bending test, a_(sp) was set at 77mm, a_(r)=25 mm, and the length of the actuator 105, a_(l) was set at190 mm. Only a single bending actuator 105 on the module 100 wasinflated up to 241.3 kPa. The module 100's maximum bending payload witha single bending actuator 105 inflated was 7.63+/−1.2 N and the maximumbending angle observed was 148.7+/−0.61°.

Twisting Performance

In some exemplary embodiments, by varying the length of the actuators105 (a_(l)), module 100 was able to twist up to 201.62+/−9.33°,193.14+/−1.17°, or 208.99+/−1.08° at 243.1 kPa, respectively. We noticethat the twisting performance of module 100 was unaffected by the changein length of the actuators 105, as seen in FIG. 8A.

Varying the spacing between the actuators 105, as shown in FIG. 8B, didnot affect the final twisting angle of the actuator 105 at 241.3 kPa.But it was noticed that by placing the actuators 105 slightly furtherapart at a_(sp)=77 mm, module 100 was twisting more until about 206.8kPa. For actuators 105 with a radius of a_(r)=20 mm and a_(r)=25 mm, thetwisting angles at 241.3 kPa were 193.14+/−1.17° and 230.36+/−3.70°respectively. The actuator 105 with a radius of a_(r)=25 mm showed abetter overall twisting performance. Therefore, in various exemplaryembodiments, in module 100 the maximum actuator radius for an actuator105 with a length of 190 mm is selected to be approximately 25 mm.

Contracting Performance

In some exemplary embodiments, by varying a_(l), it highlighted similarcontraction length between modules 100 configured with a_(l)=190 mm anda_(l)=210 mm, with contraction of 102.28+/−1.08 mm and 97.10+/−0.46 mmat 241.3 kPa, respectively, as seen in FIG. 10A. However, module 100with a_(l)=190 mm only had a contraction length of 77.77+/−1.47 mm.

The change in a_(l) also affected the contraction force of exemplarymodules 100, as seen in FIG. 10D. The maximum contraction payloadcapacity was respectively 16.89+/−1.73 N, 22.07+/−0.28 N, and19.8667+/−0.48 N for a_(l)=170 mm, 190 mm and 210 mm. It will beappreciated that in these operations for module 100, before creating acontraction pulling force, module 100 extends very slightly, creating apushing force of −27.5+/−1.11 N, −27.2+/−0.48 N, and −14.1+/−0.83 Nrespectively. This highlights that an exemplary module 100 with thelongest actuators (a_(l)=210 mm), shows the smallest pushing forcebefore starting to contract.

As shown in FIG. 10B, the larger the spacing distance between actuators105, the more module 100 contracts. At 206.8 kPa, module 100 witha_(sp)=22 mm and a_(sp)=77 mm had the contracting lengths of89.37+/−3.78 mm and 102.28+/−1.09 mm, respectively. The change inspacing between the actuators 105, a_(sp), showed less of an effect onthe contraction force of the module 100, seen in FIG. 10E. Thus, module100 with a_(sp)=22 mm and a_(sp)=77 mm had contract forces of 24+/−1.29N and 22.07+/−0.28, respectively.

Similar to the twisting performance, in some embodiments module 100 withthe largest actuator 105 radius (a_(r)=30 mm) was not able to contractas the pressure increased as well, seen in FIG. 10C. We also observedthat module 100 with a_(r)=20 mm and a_(r)=25 nm had contracting lengthsof 102.28+/−1.09 mm and 93.71+/−2.67 mm at 241.3 kPa, respectively.Module 100 with a_(r)=25 mm achieved the maximum contracting lengthearlier at 172.4 kPa, showing a better overall contracting mobilityperformance.

In some configurations, module 100 having a large actuator 105 radiusmay not be able to contract, for example as seen in FIG. 10F. We alsosaw a larger contraction force of 61.65+/−3.33 N for module 100 witha_(r)=25 mm compared to module 100 with a_(r)=20 mm with a contractionforce of 22.07+/−0.28V at 241.3 kPa.

In various exemplary embodiments, module 100 may be utilized to graspand manipulate objects.

Bionic Winding Manipulator: The twisting and contracting motion profileof exemplary module 100 highlighted a unique grasping methodology usingbionic winding, for example as seen in FIG. 11 . In this graspingmethodology, the object to be grasped is placed between the actuators,and then the twisting actuators contract to grasp the object. Graspingperformance of module 100 was demonstrated by grasping three differenttypes of objects with different weights, sizes and textures. A ball(25.7 g), a wooden block (240.5 g), and a plastic water bottle (500.4 g)were grasped, manipulated, and thereafter released, shown in FIG. 11 .

In an exemplary embodiment, a method 1200 for grasping an objectcomprises: providing a module 100 comprising three inflatable actuators(step 1202); moving module 100 such that the object is disposed at leastpartially between at least two of the actuators (step 1204); inflatingthe inflatable actuators to cause module 100 to twist and contract (step1206) to grasp the object. Method 1200 may further comprise movingmodule 100 to move the object (step 1208); and deflating the inflatableactuators to release the object (step 1210). The steps may be repeated,as desired, in order to repeatedly manipulate an object or manipulatemultiple objects in turn.

Soft Robotic Wrist: In various embodiments, module 100 may be operableas a soft robotic wrist, for example for twisting to uncap and cap abottle, as seen in FIG. 11 . A plate with a cut out with the same radiusof the bottle cap was attached to the end of the actuator. When themodule is pressed against the bottle cap a snug fit is established.Then, by inflating the actuators module twists to uncap the bottle, forexample in a counter-clockwise motion. To cap the bottle again, theactuators in the module are deflated, creating a clockwise motion. Thus,any suitable twisting motion or application may be implemented viaattaching an appropriate end-effector to module 100.

Soft Continuum Robotic Arm: To assemble an exemplary soft continuumrobot arm (SCRA), connector pieces at the end of each soft module may bedesigned to easily attach and detach to each other, for example usingnuts and bolts. Exemplary modules 100 utilized herein were made ofactuators with a length of 190 mm, to combine to create a SCRA with alength of approximately 590 mm. In some exemplary embodiments, the SCRAmay implement bending and contracting, for example as seen in FIG. 9 .In one embodiment, the full arm was able to contract to approximately301 mm, which is approximately 48.98% contraction in total.

Principles of the present disclosure emphasize the design,characterization, and evaluation of a new soft continuum module thatutilized only 3 actuators to be able to perform multi-axis bending and acoupled motion of helical twisting and contracting. The geometricalparameters of the module may be selected based on how the length andradius of the actuators and spacing between them affect the motion andpayload of the module, when inflated with an input pressure. Exemplaryembodiments utilize the disclosed actuator as a bionic windingmanipulator and soft continuum robot arm.

While the principles of this disclosure have been shown in variousembodiments, many modifications of structure, arrangements, proportions,the elements, materials and components, used in practice, which areparticularly adapted for a specific environment and operatingrequirements may be used without departing from the principles and scopeof this disclosure. These and other changes or modifications areintended to be included within the scope of the present disclosure.

The present disclosure has been described with reference to variousembodiments. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the present disclosure. Accordingly, the specification is to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent disclosure. Likewise, benefits, other advantages, and solutionsto problems have been described above with regard to variousembodiments. However, benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential feature or element.

As used herein, the terms “comprises,” “comprising,” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises a list ofelements does not include only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Also, as used herein, the terms “coupled,”“coupling,” or any other variation thereof, are intended to cover aphysical connection, an electrical connection, a magnetic connection, anoptical connection, a communicative connection, a functional connection,and/or any other connection. When language similar to “at least one ofA, B, or C” or “at least one of A, B, and C” is used in thespecification or claims, the phrase is intended to mean any of thefollowing: (1) at least one of A; (2) at least one of B; (3) at leastone of C; (4) at least one of A and at least one of B; (5) at least oneof B and at least one of C; (6) at least one of A and at least one of C;or (7) at least one of A, at least one of B, and at least one of C.

What is claimed is:
 1. A method for manipulating an object, the methodcomprising: providing a soft continuum robotic module, wherein themodule comprises three inflatable actuators disposed between and linkinga top plate and a base plate; Moving the soft continuum robotic moduleto place the object at least partially between at least two of theinflatable actuators; and inflating the three inflatable actuators tocause the soft continuum robotic module to twist and contract and applya grasping force between the inflatable actuators and the object.
 2. Themethod of claim 1, further comprising manipulating the object by movingthe soft continuum robotic module.
 3. The method of claim 2, furthercomprising releasing the object by deflating at least one of the threeinflatable actuators.
 4. The method of claim 3, further comprising:moving the soft continuum robotic module to place a second object atleast partially between at least two of the inflatable actuators; andinflating the three inflatable actuators to cause the soft continuumrobotic module to twist and contract and apply a grasping force betweenthe inflatable actuators and the second object.
 5. The method of claim1, wherein each inflatable actuator comprises: a conductive knit fabricfor use as a sensor; a first layer of thermoplastic polyurethane (TPU);a TPU-coated nylon reinforcement layer; a second layer of TPU; a knitstretch textile; and a heat-sealed TPU actuator.
 6. The method of claim5, wherein each inflatable actuator is configured with a length ofbetween 170 millimeters and 210 millimeters.
 7. The method of claim 1,wherein the soft continuum robotic module further comprises: aninflation component to inflate and deflate the inflatable actuators; anda stretch sensor disposed on at least one of the three inflatableactuators in order to characterize movement and/or positioning of thesoft continuum robotic module.
 8. A method for twisting a cap withrespect to a bottle, the method comprising: providing a soft continuumrobotic module, wherein the module comprises three inflatable actuatorsdisposed between and linking a top plate and a base plate; pressing thesoft continuum robotic module against the bottle to place the cap intocontact with the top plate; and inflating the three inflatable actuatorsto cause the soft continuum robotic module to twist and cause the cap totwist with respect to the bottle.
 9. The method of claim 8, wherein thetop plate comprises a cutout having a radius corresponding to a radiusof the cap, and wherein the cap contacts the cutout.
 10. The method ofclaim 8, wherein each inflatable actuator comprises: a conductive knitfabric for use as a sensor; a first layer of thermoplastic polyurethane(TPU); a TPU-coated nylon reinforcement layer; a second layer of TPU; aknit stretch textile; and a heat-sealed TPU actuator.
 11. The method ofclaim 8, wherein each inflatable actuator is configured with a length ofbetween 170 millimeters and 210 millimeters.
 12. The method of claim 8,wherein the soft continuum robotic module further comprises: aninflation component to inflate and deflate the inflatable actuators; anda stretch sensor disposed on at least one of the three inflatableactuators in order to characterize movement and/or positioning of thesoft continuum robotic module.